The present invention relates generally to air-oil separators useful for separating oil from an entering air-oil mixture and, more specifically, to an air-oil separator mounted remote from an engine air filter and comprising a serviceable oil coalescing filter for separating oil in a vacuum regulated environment.
Increasingly stringent environmental regulations, and a heightened consciousness of environmental conservation, has mandated cleaner operation of hydrocarbon powered sources such as automobiles, boats, trucks, motorcycles, or the like. As a result, blow-by devices such as pollution control valves have become required standard equipment for all automobiles. These blow-by devices capture air-oil emissions from the crankcase of a hydrocarbon burning internal combustion engine and direct them in a closed system to the engine air intake system for subsequent combustion. The emissions generated from the crankcase of diesel engines, for example, are heavily ladened with oil and other heavy hydrocarbons. Accordingly, devices, such as air-oil separators, have been developed in an effort to make the operation of such engines cleaner and more efficient. These devices are designed to filter inlet air routed to an intake of an engine, separate oil and other hydrocarbons emitted from a contaminated engine atmosphere, and regulate the pressure within an engine crankcase.
Typical air-oil separators are designed to both filter air prior to entering an engine intake system, and separate an air-oil mixture received from an engine crankcase into its liquid and gas constituents. Such air-oil separators have an inside chamber or portion that is configured to mechanically separate oil from the entering air-oil mixture. More specifically, such air-oil separator includes a primary air inlet that is connected to an engine intake system, and that creates an internal vacuum within the device for receiving the air-oil mixture. The air-oil mixture is passed through one or more internal baffles and/or filter material for effecting oil separation. The separated oil component is collected and removed from the separator for either further treatment or for routing back to an engine crankcase. The separated air component is directed to the primary air inlet and into the engine intake system for combustion.
Such intake mounted air filter/air-oil separators are ideally operated in conjunction with a vacuum limiting device that serves to prevent the pressure differential between the separator and engine crankcase from reaching a predetermined maximum. The use of a vacuum limiting device helps to prevent the unwanted carryover and passage of oil from the crankcase into the separator under operating conditions of a large pressure differential between the separator and crankcase.
Air filter/air-oil separator devices comprising external vacuum limiting devices are known in the art, wherein the vacuum limiting device is positioned between an air-oil mixture inlet into the separator and the crankcase. While such external vacuum limiting devices do function to limit/control the amount of vacuum that is directed to the engine crankcase from the separator, the placement such a vacuum limiting device external from the separator causes the inside portion of the separator to be subjected to a relatively high unregulated vacuum of in the range of from about 10 to 35 inches. Thus, the only portion of a system comprising such an external vacuum limiting device that operates within a vacuum regulated environment is the engine crankcase.
A result of such uncontrolled vacuum within the separator is that the air-oil mixture entering the separator for separation is directed through the housing at a relatively quick velocity, thereby reducing the reduced residence time of the mixture within the housing and limiting air-oil separation efficiency. Additionally, the relatively large vacuum maintained within the separator during the course of operation tends to limit the oil removal efficiency from the separator due to a cavitation-like effect that impairs gravity drainage of the collected oil from the separator.
Previous attempts have been made to design air-oil separators to address the problem described above. One such system is described in U.S. Pat. No. 5,564,401, the disclosure of which is incorporated herein by reference. This patent discloses a closed crankcase emission control assembly comprising pressure-control assembly, a filter, and an oil drain check valve. The assembly is generally configured having an inlet passage, a pressure control assembly disposed downstream of the inlet passage, a filter channel disposed downstream of the pressure control assembly, a barrier filter positioned within a filter housing and downstream from the filter channel, and an outlet passage positioned downstream from the barrier filter. This device is designed to be mounted remote from an engine intake system, and is configured with its inlet passage connected to an engine crankcase for receiving an air-oil mixture, and its outlet passage connected to an engine intake system.
Configured in this manner, the patented device operates to receive an air-oil mixture from an engine crankcase into its inlet passage, pass the mixture through its pressure-control assembly and through the barrier further where the oil constituent is separated and collected for removal, and pass the separated air constituent out of the device via the outlet passage. However, this device suffers from the same problem noted above; namely, that the pressure-control assembly is positioned upstream from the barrier filter so that inside portion of the device is not disposed within a vacuum regulated environment. Rather, the only portion of the device that is subjected to a vacuum regulated environment is the inlet passage. Thus, this device too suffers from the air-oil separation and oil removal inefficiencies described above.
There is, therefore, is a need to provide an air-oil separator that is configured having an air-oil separation chamber subjected to a vacuum regulated environment to increase air-oil mixture residence time therein for purposes of further increasing air-oil separation efficiency. It is further desired that an air-oil separator be configured having a vacuum regulated environment for purposes of increasing oil removal efficiency by gravity drainage. It is also desirable that the device be constructed in a manner that allows it be positioned at a location remote from the engine and other high-temperature components, be easy to install and use without a need for special equipment or instruction, and be serviceable to extend the useful service life of the device.
The present invention comprises a remote air-oil separator for use with internal combustion engines for imposing a slight vacuum onto an engine crankcase and separating an air-oil mixture removed from the crankcase into its air and oil constituents for further treatment or for respective recombination with intake air for combustion and replacement into the engine crankcase. Air-oil separators of this invention are remote in that they are configured to be placed and/or attached separate from an engine intake housing, and have a vacuum regulated environment to provide improved air and oil separation efficiency over conventional air-oil separators.
Air-oil separators of this invention comprise a housing having an internal chamber defined by a housing sidewall surface that extends axially from a housing base to a housing open end. The open end includes a removable lid disposed thereon. The housing includes an inlet for receiving an air-oil mixture into the internal chamber from an internal combustion engine, and an outlet for passing a separated air stream from the internal chamber and out of the housing. An oil coalescing filter element is removably disposed within the internal chamber and is positioned/interposed between the inlet and outlet. Means for controlling a pressure differential within the housing internal chamber between the inlet and outlet is positioned downstream from the filter and in communication with the outlet and a vacuum generating source.
The means for controlling can be mounted onboard or off board the separator and is configured to impose a controlled amount of vacuum within the housing, i.e., provide a regulated vacuum environment, to control the volumetric flow rate and residence time of the air-oil mixture through and within the housing and filter element. Thus configured, air-oil separators of this invention provide improved air and oil separation efficiencies when compared to conventional air-oil separators. Air-oil separators of this invention can be used in conjunction with onboard or off board prefilters disposed within the air-oil mixture flow path upstream of filter element that functions as a first stage filtration element to the primary oil coalescing filter element to improve the service life of the primary filter element.